This invention relates to refrigerating method and refrigerating apparatus of showcases for foodstuff displaying use or goods containing cases of automatic vending machines and the like, more specifically method and apparatus being suitable especially for refrigerating of cold storage or refrigerating showcases installed for example in large scale markets, as well as open type showcases and vending machines utilizing said refrigerating method and apparatus.
Nowadays when the scale-up of foodstuff shops or markets is advancing due to lightening of the Large Scale Shops Regulation, production of refrigerated or chilled foodstuff is more and more increased in our foodstuff industry. As a result, showcases for refrigerated foodstuff and cold-storage foodstuff (these showcases for refrigerated and/or cold-storage foodstuff being called hereunder "showcases") are occupying more and more proportion of the available floor surface of these shops.
These showcases are to refrigerate or cold-store the foodstuff contained therein by means of cold air refrigerated through refrigerating units constituting a refrigerating circuit. The refrigerating units comprise various members such as a compressor, a condenser, expanding members and an evaporator constituting a refrigerating cycle and connected to each other through a piping in which a coolant is circulated, and a fan serves to carry out heat-exchange between coolant in the evaporator and surrounding medium for refrigerating said medium.
The operation of the refrigerating cycle is as follows:
Coolant is first absorbed into the compressor and compressed therein to a condition of high temperature--high pressure. Coolant in this condition is forced to pass through a condenser such as for example capillary tubes and wherein coolant is subjected to heat-exchange with surrounding air thereby to cause the medium to radiate and liquefy. Liquid coolant thus obtained is subjected to adiabatic expansion at expansion members such as expansion valve thereby to be changed into liquid condition of low temperature--low pressure. Coolant in this liquid condition is caused to pass through the evaporator to absorb heat from surrounding medium to be refrigerated, thereby to refrigerate said surrounding medium while at the same time evaporating itself to return to its initial gas condition. Then coolant in its gas condition is again absorbed into the condenser for continuing the refrigerating cycle.
The refrigerating apparatus of conventional showcases is now explained below.
The conventional showcases installed in the shops contained therein the above described expansion members, evaporator, fans and various controllers. On the other hand, said compressor with its driving motor was set in a machinery room set outdoor, and said condenser was set in a ventilated place such as on the roof. These compressor and condenser installed outdoor and said expansion members and evaporator contained in each showcase were connected each other through a plurality of (coolant) pipings.
In particular, for connecting said compressor to various mechanical members, use was made of a plurality of pipings which were to be laid so as to connect branches from the side of said compressor to each showcase while preventing leakage of coolant therefrom. Connecting means for the pipings consisting of copper pipes were welding between adjacent pipes or mechanical joint members such as screw. Further, the outer surface of each pipe was covered by adiabatic members.
In the above refrigerating device, high temperature--high pressure coolant fed from said compressor through said pipings was caused to evaporate in the evaporator contained in the showcase to cause heat-exchange with air in the goods displaying portion of the showcase thereby to refrigerate these goods.
Since temperature of the surface of evaporator for carrying out heat-exchange with air in the goods displaying portion in the showcase is generally below ice point, frost is formed on the surface of evaporator. Consequently, frost removing operation called "Defrosting" was carried out at the frequency of one time for 3-4 hours. This defrosting operation is to remove frost on the surface of evaporator by interruption of cooling cycle in the showcase. Therefore, a drain pipe had to be set in each showcase for draining waste water resulting from said defrosting operation.
The installation of showcases needs various large works such as coolant pipings, covering of adiabatic members on the pipings, and drain piping for each showcase as well as electrical operation for feeding electricity to each showcase. As a result, once installed, the showcases could not be shifted easily due to the drain pipes and electrical distributing cables, and the replacement of showcases were fairly expensive work.
When the connection of said pipings were carried out through welding in said coolant piping works, there was a risk of pipe damages under excessive charges applied to the connection due to any outer shocks. In the case of screw connection of said pipings, contraction of pipes such as copper pipe due to variation of temperature caused loosening of screws. In any case, leakage of coolant such as freon gas generates serious environmental problems since freon gas causes the destruction of ozone layer. Further, since the number of connections of said pipings were increased together with the number of showcases, with the result of higher leakage of coolant and more complicated maintenance works.
Further, when the above described defrosting has been carried out for removing frost deposited on the evaporator, it was inevitable that the temperature in showcase was increased by 10-15 degrees centigrade. But the increase of temperature caused generally the problems of quality control such as drip dropping or so called "dripping" of raw meat or raw fish maintained in a chilled condition. On the other hand, in the event of trouble with machines in the showcase, repairing works must have been done in the shop with corresponding business delay.
On the other hand, concerning to a large number of vending machines located all over the country and having each refrigerating unit therein, problems similar to those of showcases have occurred especially when a plurality of such vending machines were installed in the same place.
Moreover, the conventional showcase installed in the shop has a goods take-out port which is opened on the front surface thereof. Cooled air in the showcase flows out through the port and the cooled air stays on the passage in front of the showcase. Accordingly, the cooling efficiency of the showcase is bad and a person who passes by the showcase or takes out some goods from the showcase feels cold on his feet.